Refrigeration system evaporator

ABSTRACT

The evaporator includes a heat exchange element adapted to be filled with liquid refrigerant and a surge drum disposed ab ove the element. A first duct connects the drum interior to an inlet at the lower end of the heat exchange element, and a second duct connects an outlet, adjacent the upper end of the heat exchange element, to the drum interior. A high pressure liquid ejector is included in the first duct and a refrigerant supply valve controls the supply of high pressure liquid refrigerant to the ejector. A float valve control means opens and closes the supply valve responsive to variation of liquid level in the drum, and high pressure liquid fed to the ejector entrains refrigerant to flow from the drum to the heat exchange element. An adjustable threaded needle controls flow to the jet nozzle. The drum has a refrigerant vapor suction line outlet, and an oil pick-up tube extends from a point near the bottom of the interior of the drum to the suction line outlet.

United States Patent [1 1 Merryfull 1 REFRIGERATION SYSTEM EVAPORATOR [76] inventor: Albert Edward Merryfull, l7 Ayres Rd. East, St. lves, N. S. W., Australia [22] Filed: Mar. 29, 1972 [21] Appl. No.: 239,159

[30] Foreign Application Priority Data Mar. 31, 1971 Australia 4465 [52] US. Cl 62/218, 62/84, 62/500 [51] Int. Cl. ..'F25b 41/04 [58] Field of Search 62/218, 500, 84

[56] References Cited UNITED STATES PATENTS 320.308 6/1885 Suckcrt 62/84 1,836,318 12/1931 Gay 62/500 1,994,037 3/1935 Gay 62/218 2,512,869 6/1950 McBroom.... 62/500 3,070,977 1/1963 Kimmel 62/84 3.283.532 11/1966 Kocher 62/84 Jan. 1, 1974 Primary Examiner-William J. Wye Attorney-John J McGlew et a1.

[ 57] ABSTRACT The evaporator includes a heat exchange element adapted to be filled with liquid refrigerant and a surge drum disposed ab ove the element. A first duct connects the drum interior to an inlet at the lower end of the heat exchange element, and a second duct connects an outlet, adjacent the upper end of the heat exchange element, to the drum interior. A high pressure liquid ejector is included in the first duct and a refrigerant supply valve controls the supply of high pressure liquid refrigerant to the ejector. A float valve control means opens and closes the supply valve responsive to variation of liquid level in the drum, and high pressure liquid fed to the ejector entrains refrigerant to flow from the drum to the heat exchange element. An adjustable threaded needle controls flow to the jet nozzle. The drum has a refrigerant vapor suction line outlet, and an oil pick-up tube extends from a point near the bottom of the interior of the drum to the suction line outlet.

4 Claims, 3 Drawing Figures PATENTED H974 3 782 131 SHEET 1 OF 3 F/gJ.

PATENTEU 1 I974 SHEET 2 BF 3 VA fw I REFRIGERATION SYSTEM EVAPORATOR FIELD AND BACKGROUND OF THE INVENTION This invention relates to refrigeration systems of the kind having a fully flooded refrigerant evaporator. That is to say systems wherein the evaporator is substantially filled with liquid refrigerant when in operation.

Conventionally the evaporator of such a system is pipe or duct connected to a surge drum partially filled with liquid refrigerant. The drum is disposed so that the liquid surface level in the drum is above the evaporator to keep the evaporator full of liquid. In use, the systems compressor draws refrigerant vapour from the surge drum and after compression and condensation the refrigerant liquid is delivered to the high pressure or inlet end of the evaporator.

- SUMMARY'OF THE INVENTION An object of the present invention is to provide very simple means for (a) maintaining a high refrigerant flow rate through the evaporator, to scrub vapour bubbles from the interior surfaces of the evaporator as they form, and (b) regulating the supply of high pressure primary liquid to the evaporator to maintain the liquid level constant as the refrigerant evaporates.

The invention consists in a refrigeration system evaporator comprising a heat exchange element adapted to be filled with liquid refrigerant, a surge drum, a first duct connecting the interior of the drum to an inlet of the heat exchange element, a second duct connecting an outlet of the heat exchange element to the interior of the drum, a high pressure liquid ejector associated with the first duct, a refrigerant supply valve controlling the supply ofhigh pressure liquid refrigerant to the ejector and valve control means to open and close the valve in response to variation of liquid level in the drum. The ejector being such that high pressure liquid feed to it causes refrigerant to flow from the drum to the heat exchange element by entrainment therewith.

Thus it will be seen that the ejector, supply valve and valve control means operate to keep the liquid level constant and at the same time cause liquid to circulate from the drum, through the heat exchange element and back to the drum.

For preference the supply valve and valve control means are combined as a single unit in the form of a float operated valve of the kind customarily used to maintain a constant level in a cistern or the like. However, instead of discharging into the drum, the valve output is piped to an injector in the first duct, thereby agitating and moving the liquid within the heat exchange element. Such movement is beneficial not only because it scrubs vapour bubbles from the heat exchange surface so permitting fuller contact between that surface and the liquid refrigerant but also because it tends to keep the heat exchange surfaces clean of oil which otherwise tends to adhere thereto and so reduce the efficiency of heat transfer.

BRIEF DESCRIPTION OF THE DRAWINGS By way of example an embodiment of the above described invention is described hereinafter with reference to the accompanying drawings:

FIG. I is a schematic diagram of a refrigeration system evaporator according to the invention,

FIG. 2 is a longitudinal sectional view through a high pressure liquid ejector, being a component of the evaporator of FIG. 1,

FIG. 3 is a longitudinal sectional view of a refrigerant supply valve, being a component of the evaporator of FIG. ll.

DESCRIPTION OF THE PREFERRED EMBODIMENT The illustrated evaporator comprises a heat exchange element 4, a surge drum 5, a first duct 6 connecting the interior of the drum 5 to the inlet of the heat exchange element 4, a second duct 7 connecting an outlet of the evaporator 4 to the interior of the drum 5, a high pressure liquid ejector 8 associated with the duct 6, and a refrigerant control valve 9.

The heat exchange element 4 may be of any conventional fully flooded type usable to cool a medium by heat exchange between the medium and the refrigerant within the heat exchange element 4. For example, it may be a hollow plate type evaporator.

The surge drum 5 may also be conventional in nature and is disposed above the heat exchange element 4. In many cases it may be supported by the heat exchange element 4.

In use the drum 5 is continuously evacuated by way of an exhaust outlet 10 adapted to be connected to the inlet or suction side of a refrigerant compressor. The drum preferably has a sump 11 which in use contains liquid refrigerant 12 while the remainder of the drum contains refrigerant vapor.

For preference, a fine bore oil pick-up tube 35 extends from the exhaust outlet 10 to the floor of the drum 5. This is provided for the pick-up of oil which may be in the liquid refrigerant (and then appears as a film floating on the surface of the refrigerant) for return of that oil to the compressor.

The second duct 7 may be a conventional pipe con nection between the drum 5 and the evaporator 4. Likewise the first duct 6 throughout most of its length may be a conventional pipe linebut also includes a hollow casing 13 of the ejector 8.

The ejector 8, as best seen in FIG. 2, comprises the casing 13 housing ajet nozzle 14. The jet nozzle 14 is directed towards an outlet opening in the casing 13 from which a pipe 15 extends to the heat exchange element 4 and the annular space 16 surrounding the nozzle 14 is connected by pipe 6 to the drum 4. Thus the casing 13 in effect constitutes a part of said first duct, with the nozzle 14 extending longitudinally thereof.

It will be clear from the foregoing that primary or high-pressure liquid fed to the ejector 8 to flow from the nozzle will entrain secondary or low pressure liquid with it to cause flow along the first duct 6.

For preference, the ejector 8 has a screw-adjustable needle 16 controlling flow to the jet nozzle 14 or other valve device in series with the nozzle 14 whereby the flow characteristics of the jet nozzle may be adjusted to suit any particular installation. If a screw-adjustable needle 16 is present, the ejector casing 13 may include a closure cap 17 at one end which may be removed to give access to the needle 16.

The control provided by the needle 16 renders the quantity of refrigerant in the system less critical than it is in prior-known systems using injectors. In such priorknown systems the injector has a fixed orifice and control of the amount of liquid refrigerant boiling within the evaporator requires the system as a whole to be charged with an accurately determined quantity of refrigerant and for the amount of refrigerant to be maintained constant throughout the operating life of the system. In the present instance the quantity ofliquid in the evaporator is controlled without reference to stored liquid in the system as a whole.

Primary or high pressure liquid refrigerant is fed to the ejector 8 by way of high pressure supply line 18 under the control of the supply valve 9.

High pressure liquid from the systems condenser is fed to the valve 9 preferably by way of a heat exchange tube 19 within the vapour space inside the surge drum 5.

The control valve 9, as best seen in FIG. 3 comprises an internally threaded inlet port 20 opening to the interior of a cylinder body 21 through an annular valve seat 22. Flow through the valve seat 22 is controlled by a tapered valve element 23 movable as one with a piston 24.

For as long as the valve element 23 is in sealing contact with the seat 22, flow through the valve is prevented but when the valve element 23 departs from the seat 22, flow to the ejector 8 may occur through outlet port 25 and the supply line 18.

A constricted passageway 26 extends through the piston 24 so as to pressurise space 27 behind the piston. When the space 27 is pressurised a loading spring 28 suffices to keep the valve element 23 in contact with the seat 22 against the supply pressure but if the pressure in the space 27 drops, the spring 28 is no longer able to withstand the supply pressure.

The fluid pressure within the space 27 is controlled by way of a pilot valve 29 comprising an annular pilot valve seat 30 and a pilot valve element 31.

The position of the pilot valve element 31 is determined by an operating lever 32 fulcrumed at 33 and supported at its free end by a float 34 floating on the liquid 12 in the sump 11. Thus should the liquid level in the sump fall, the pilot valve 29 opens to relieve the fluid pressure in the space 27, thus enabling valve element 23 to move from the seat 22 to supply primary liquid to the evaporator inlet until such time as the liquid level in the sump rises to its normal position.

In practise there is more or less continuous infeed of primary liquid to compensate for the removal of refrigerant from the evaporator as vapour.

I claim:

1. A refrigeration system evaporator comprising a heat exchange element adapted to be filled with liquid refrigerant, a surge drum disposed above said element, a first duct connecting the interior of the drum to an inlet at the lower end of the heat exchange element, a second duct connecting an outlet adjacent the upper end of the heat exchange element to the interior of the drum, a high pressure liquid ejector associated with said first duct, a refrigerant supply valve controlling the supply of high pressure liquid refrigerant to said ejector and valve control means operable to open and close said valve in response to variation of liquid level in the drum; high pressure liquid fed to said ejector causing refrigerant to flow from the drum to the heat exchange element by entrainment therewith.

2. An evaporator according to claim 1 wherein said valve control means comprise a float operated pilot valve.

3. An evaporator according to claim 1 wherein said ejector comprises a jet nozzle within a hollow casing and has an adjustable needle controlling flow to the jet threaded nozzle.

4. An evaporator according to claim 1 having a refrigerant vapour suction line outlet from said drum and an oil pick-up tube extending from a point near the floor of the drum to said suction line outlet. 

1. A refrigeration system evaporator comprising a heat exchange element adapted to be filled with liquid refrigerant, a surge drum disposed above said element, a first duct connecting the interior of the drum to an inlet at the lower end of the heat exchange element, a second duct connecting an outlet adjacent the upper end of the heat exchange element to the interior of the drum, a high pressure liquid ejector associated with said first duct, a refrigerant supply valve controlling the supply of high pressure liquid refrigerant to said ejector and valve control means operable to open and close said valve in response to variation of liquid level in the drum; high pressure liquid fed to said ejector causing refrigerant to flow from the drum to the heat exchange element by entrainment therewith.
 2. An evaporator according to claim 1 wherein said valve control means comprise a float operated pilot valve.
 3. An evaporator according to claim 1 wherein said ejector comprises a jet nozzle within a hollow casing and has an adjustable needle controlling flow to the jet threaded nozzle.
 4. An evaporator according to claim 1 having a refrigerant vapour suction line outlet from said drum and an oil pick-up tube extending from a point near the floor of the drum to said suction line outlet. 